Centrifugal pump shaft power
Thread Content
When selecting a centrifugal pump, the shaft power is calculated based on the operating conditions at the pump’s rated point, thereby determining the power required for the motor. So, is it possible that, when the pump is operating on-site and at a low flow rate, its efficiency being too low may result in the shaft power exceeding the motor’s power, thereby causing an overcurrent condition?
It won’t happen. It is recommended that you check the curves for flow rate versus head, flow rate versus power, and flow rate versus net positive suction head. The power of a centrifugal pump increases as the flow rate increases, and it decreases when the flow rate drops.
It’s impossible… Efficiency follows a fixed curve: low flow means low output power, and thus low shaft power as well…
No, the flow rate is low, so the shaft power is also low.
There is a pump on site with a specific gravity of 0.6; the water tests before leaving the factory showed no problems, but during operational testing on site, when the flow rate reached around 4 cubic meters, the motor experienced overcurrent. After removing the pump, I checked the ring and bearings – there were no problems, and the alignment was good; it’s strange!
Take out the \"Performance Curve for Normal Temperature Clean Water\" for this pump and compare it to see if it is a problem with the selection.
Reply to 1# modouyu123: The pump is driven by a motor, and the energy for the pump comes from the motor. Do you think it could be greater?
Reply to 5# modouyu123: It’s likely that the pump was not designed based on the specific gravity of water
Reply to 6# w6861938: I have analyzed both the expected performance curve and the actual experimental performance curve. Based on the curves provided by the manufacturer, the shaft power was calculated for the low-flow point and the rated point, and the motor power selected is appropriate. However, during the on-site water test, when the flow rate reached 4 cubic meters (with a rated flow rate of 13 cubic meters), an overcurrent condition occurred, causing the motor to stop. Moreover, the manufacturer also conducted a water test before shipping the product, and it worked fine there; so why did an overcurrent occur once it was at the installation site?
Reply to 5# modouyu123: Centrifugal pump. When the pump operates at low flow rates, its efficiency is low, but this does not cause the shaft power to exceed the motor’s capacity, resulting in overcurrent. I’m not aware of the model and technical specifications of your pump and motor, so it’s difficult to determine the cause.
Reply to 10# hcwang12345: Fixed point: Q=13.3, H=43, efficiency 30%; low-flow point: Q=4, H=46, efficiency 13%. Motor power: 5.5 KW, speed: 1450 r/min. It is a horizontal cantilever pump with 4 speed stages.